Am I wrong for this ?

So I’ve been with my partner for almost 7 years & the past year we had a bump in the road. Let’s just say it involved another female . We’ve been trying to move on a heal from that very dramatic situation , but the girl still tries to keep in touch with his family on social media & I did find out they had been in communication within this year of “healing” . He claims that after I seen that he’s block her and told her that he’s with me and there’s nothing going on with them . About a week ago . I see on social media that she liked a post of his and he liked hers back . He summed it up to be that’s he’s been really stressed and trying to figure out his life & it has his doing “dumb things”. I’ve been telling him that the only way I will come back is if I see him tell her he wants nothing to do with this girl and let her know to leave you alone and respect what is being said to her .. however it’s been a fight about that as if he doesn’t want to tell her. He claims it will start drama & he just wants to continue moving on but I don’t see how saying what needs to be said and REALLY blocking someone will start drama . It’s all so disappointing .. am I wrong for giving a ultimatum ? & how do I get my point across that this isn’t right ?